Do Protein Shakes Cause Weight Gain?
Learn about protein shake benefits, types, and best practices for fitness, weight management, and health, plus potential side effects and nutritional insights.

Protein shakes offer concentrated nutrition, appealing to athletes and casual exercisers alike. These shakes typically consist of protein powder mixed with water, milk, or another liquid. They come in powder form for self-mixing or as ready-to-drink options. Each shake usually contains 10 to 30 grams of protein, sourced from dairy, eggs, or plants. Besides protein, these shakes may include added sugars, artificial flavors, vitamins, and minerals.
Various protein types are used in these shakes:
- Whey protein: Derived from cow’s milk, absorbs quickly, making it ideal for muscle recovery.
- Casein: Also milk-based, digests slowly, providing a steady release of amino acids.
- Soy protein: Plant-based and versatile, offering all essential amino acids.
- Pea protein: Hypoallergenic and easily absorbed, though slightly low in cysteine and methionine.
- Hemp protein: Rich in omega fatty acids and complete in its amino acid profile, but its digestibility can vary.
- Rice protein: Lacks lysine but is gentler on the stomach.
Nutritionally, protein shakes can be beneficial. A typical shake provides protein along with carbs, fats, and sometimes fiber. The protein content supports muscle repair and growth, while carbs and fats offer energy. Many shakes are also rich in vitamins and minerals, like iron and calcium.
These shakes are consumed in various ways. Many drink them post-workout to aid muscle recovery. Some use them as meal replacements or snacks to increase protein intake. Mixing them with water, milk, or plant-based milk is common, but blending them into smoothies with fruits or vegetables adds extra nutrients and flavor.
Protein Shakes and Weight Management
Protein shakes can be both beneficial and challenging for weight management, depending on how they’re incorporated into your diet. They can assist in weight loss by promoting satiety and aiding muscle growth. Protein has been shown to help people feel full longer compared to carbohydrates and fats. This effect is partly due to increased levels of fullness hormones like GLP-1 and PYY.[1]
A 2020 study highlighted that consuming over 35 grams of protein in a single meal led to reduced hunger and a lower desire to eat, compared to meals with less protein.
Additionally, protein shakes can support muscle growth, an integral part of a healthy metabolism. Muscle mass requires more energy to maintain than fat, meaning that by building muscle through resistance training and sufficient protein intake, you help your body burn more calories, even at rest. This is particularly useful for those on a calorie-restricted diet.
However, consuming protein shakes without proper dietary adjustments can lead to weight gain. Protein shakes often add extra calories to your daily intake. If you aren’t careful about balancing these extra calories by eating less elsewhere or increasing your physical activity, the surplus can contribute to weight gain. This is especially true for those who consume high-calorie shakes loaded with added sugars and fats.
It’s crucial to remember that your overall dietary habits play a significant role. Relying solely on protein shakes without paying attention to the rest of your diet can backfire. Whole foods provide a diversity of nutrients and fibers that protein shakes might lack. Integrating shakes thoughtfully into a balanced diet is essential.
For optimal results, consider the timing of protein shake consumption. Post-exercise consumption, within two hours of working out, tends to maximize muscle protein synthesis. Consuming a protein shake as a meal replacement or snack can also be a strategic way to manage hunger and remain within calorie goals.
While protein shakes can certainly help manage weight by keeping you full and fostering muscle development, they are not a cure-all solution. They should be part of a comprehensive approach to nutrition and exercise. Pair them with a balanced diet full of fruits, vegetables, whole grains, and lean proteins, and maintain an active lifestyle to ensure you’re on the right track.
Recommended Protein Intake
Recommended protein intake varies depending on factors like age, sex, and activity levels. The average adult needs around 0.8 grams of protein per kilogram of body weight—roughly 0.36 grams per pound. That would equate to about 46 grams of protein daily for the average woman and 56 grams for the average man.[2]
Activity Level | Recommended Protein Intake |
---|---|
Average Adult | 0.8 g/kg body weight |
Recreational Athletes | 1.1 - 1.4 g/kg body weight |
Competitive/Ultra-endurance Athletes | Up to 2 g/kg body weight |
Older Adults | 0.6 g/lb body weight |
Protein shakes can be a convenient way to meet these elevated protein needs, particularly for those who find it challenging to consume enough protein through whole foods alone. A single shake can pack in 20-30 grams of protein, making it easier to reach your target.
Warning: While meeting your protein intake goals is crucial, it’s essential not to exceed them. Consuming more than 2 grams of protein per kilogram of body weight daily can lead to adverse effects.
- Excessive protein can strain the kidneys, particularly for those with pre-existing kidney conditions.
- It can cause digestive issues like constipation or diarrhea, especially if your diet is low in fiber.
- There’s even the risk of dehydration, as metabolizing large amounts of protein can increase water loss through urination.
Balancing your protein intake involves some skill. For most people, sticking to the recommended daily allowance should suffice. If you’re increasing your intake, ensure it’s balanced with adequate carbohydrates and fats and that it’s spread throughout the day. This balanced approach helps in efficient protein utilization and prevents metabolic overload.
Remember, protein shakes can complement your diet, but they shouldn’t become a crutch. Think of them as a convenient tool to meet your daily requirements, particularly post-workout or during a busy day. Combining them with whole foods will always be the best strategy for a balanced, healthy diet.
As you work toward your fitness or health goals, consider enlisting the help of a nutritionist or dietitian. They can customize recommendations based on your unique needs, ensuring you get the most out of your protein intake without the risks associated with overconsumption.
Potential Side Effects of Protein Shakes
While protein shakes can be a great addition to your diet, they do come with potential side effects that you should be aware of:
1. Digestive Issues
Many protein shakes, especially those derived from dairy sources like whey and casein, can cause bloating, gas, and diarrhea in people who are lactose intolerant. If you often experience these symptoms after consuming protein shakes, you might want to switch to a non-dairy alternative like pea or hemp protein.
2. Allergic Reactions
Protein shakes containing allergens like soy, eggs, or dairy can trigger allergic reactions. These reactions can manifest as rashes, swelling, a runny nose, or even more severe symptoms like difficulty breathing. Always check the ingredient list and choose protein shakes that align with your dietary needs and restrictions.
3. Exposure to Toxins
Some protein shakes might inadvertently expose you to toxins. A study by the Clean Label Project found that certain protein powders contained heavy metals like mercury, lead, and arsenic, as well as pesticides and other contaminants.[3] While these levels are generally low, consistent exposure could add up, potentially leading to health issues over time. Choosing a protein shake that has been third-party tested for purity and safety can help mitigate this risk.
4. Kidney Strain
Overconsumption of protein can pose its own set of issues. A protein intake exceeding 2 grams per kilogram of body weight daily can tax your kidneys, especially if you have pre-existing conditions. This high level of protein consumption increases the workload on your kidneys, as they have to filter out the by-products of protein metabolism.
5. Dehydration
Excessive protein can cause dehydration due to increased urine output, so staying well-hydrated is essential if you’re consuming high levels of protein.
6. Nutritional Imbalance
Beyond digestive and renal impacts, too much protein can upset your nutritional balance. High protein intake often means lower intake of other vital nutrients, such as fiber, which can lead to issues like constipation. Whole foods offer a broad spectrum of nutrients that protein shakes alone can’t provide. Consequently, it’s crucial to combine shakes with a balanced diet rich in fruits, vegetables, and whole grains.
Best Practices for Using Protein Shakes
Properly incorporating protein shakes into a balanced diet involves thoughtful planning and strategic choices. Here are some practical tips to help you maximize their benefits while avoiding common pitfalls:
- Timing is crucial. Post-workout is often the optimal time to consume a protein shake. After intense exercise, your muscles are primed for recovery and growth, and a protein shake can jump-start this process by providing the necessary amino acids. Aim to consume your shake within two hours of your workout to maximize muscle protein synthesis and recovery.
- Choose the right type of protein. If you’re looking for quick absorption and rapid muscle recovery post-workout, whey protein is a great option. For a steady release of amino acids, which can be particularly beneficial if you’re using the shake as a meal replacement, casein protein is a solid choice. Plant-based options like pea or soy protein are excellent for those who are vegan or have dairy sensitivities.
- Read labels carefully. Look for products that have been third-party tested to ensure they’re free from harmful contaminants like heavy metals and pesticides. Equally vital is choosing a shake with minimal added sugars and artificial ingredients. These additives can contribute unnecessary calories and undermine your health goals.
- Practice moderation. Protein shakes are a convenient and efficient way to boost your protein intake, but relying too heavily on them can lead to an imbalance in your diet. Remember, whole foods provide a broader array of nutrients that are vital for overall health. Integrate protein shakes as a supplement to, rather than a replacement for, your regular meals.
- Get creative with your shakes. Use your protein shakes creatively by blending them with fruits, vegetables, nuts, and seeds to create nutrient-dense smoothies. This way, you’ll also increase your fiber intake and benefit from the vitamins and minerals found in whole foods.
To prevent digestive issues, especially when first introducing protein shakes into your diet, start with smaller servings and gradually increase as your body adjusts. If you experience discomfort, consider switching to a different type of protein that might be easier on your digestive system.
Another best practice is to monitor your total daily protein intake. The goal is to meet your protein needs without overdoing it, which can strain your kidneys and lead to unwanted side effects. Spread your protein consumption evenly throughout the day to ensure optimal absorption and muscle maintenance.
Stay hydrated. Increasing protein intake can elevate the amount of water you need, as your kidneys require more water to metabolize protein’s by-products. Drinking sufficient water will help you stay hydrated and support your overall kidney health.
Incorporating protein shakes into your diet can be a valuable strategy for achieving your health and fitness goals. By balancing them with whole foods, staying mindful of your overall intake, and choosing high-quality options, you can enjoy their benefits while maintaining a well-rounded and nutritious diet.
Reference(s)
- Dhillon J, Craig BA, Leidy HJ, et al. The effects of increased protein intake on fullness: A meta-analysis and its limitations. J Acad Nutr Diet. 2016;116(6):968-983.
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press; 2005.
- Clean Label Project. 2018 Protein Powder Study. Clean Label Project website.
- Posted by Samantha Rivera